A chunk of a Denisovan skull has been identified for the first time.
It is being heralded as a dramatic contribution to the handful of known samples from one of the most obscure branches of the hominin family tree.
Paleoanthropologist Bence Viola from the University of Toronto will discuss the as-yet-unpublished discovery at the upcoming meeting of the American Association of Physical Anthropologists in Cleveland, Ohio, at the end of March.
Very little is known about the Denisovans, an extinct branch of hominins that was a sister group to Neanderthals.
Only four individual Denisovans had been identified previously, all from one cave in Siberia.
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Much about the Denisovans remains a mystery; though their existence at the site is known from fragments of bone, teeth and now skull. Only four individual Denisovans had been identified previously, all from one cave in Siberia (pictured)
The first Denisovan was described in 2010 from the fragment of a pinky finger bone, and three more were identified from teeth.
This skull piece, excavated about three years ago in that same Siberian cave, represents a fifth individual.
'It's very nice that we finally have fragments like this,' says Dr Viola. 'It's not a full skull, but it's a piece of a skull. It gives us more.
'Compared to the finger and the teeth, it's nice to have.'
But, he adds, it's hardly a full skeleton. 'We're always greedy,' he laughs. 'We want more.'
The new discovery consists of two connecting fragments from the back, left-hand side of the parietal bone, which forms the sides and roof of the skull.
Together, they measure about 8cm by 5cm (3inches by 2inches). DNA analysis proves that the piece is Denisovan, though it's too old to date with radiocarbon techniques.
Dr Viola and colleagues have compared the fragments to the remains of modern humans and Neanderthals, according to the conference abstract, although he is unwilling to discuss the details of what they learned until the work is published.
The new discovery from the Denisova cave (pictured) consists of two connecting fragments from the back, left-hand side of the parietal bone, which forms the sides and roof of the skull
Researchers have long been working to narrow down the timeline of hominin occupation at Denisova Cave. The first Denisovan was described in 2010 from the fragment of a pinky finger bone, and three more were identified from teeth (pictured) and this is the first ever discovery of a skull fragment
Researchers hope the discovery of the Denisovan skull fragment will allow for better understanding of hominin evolution and the timeline of when the earliest ancient relatives of modern-day humans migrated out of Africa
It is commonly believed that a common ancestor of Neanderthals and Denisovans migrated from Africa to Eurasia between 400,000 and 300,000
